Quick Attach Hydraulic Problem

[RedNeckRacin]

SO I finally wised up and decided to use the cabbed tractor to plow snow with. :thumbsup: I acquired a 9' meyer snow plow and fabbed up a quick attach plate to mount it. I also ran hydraulic lines from the rear scv to the front to power the angle cylinders. This is where I'm having problems. The plow angles both directions fine. My problem is when I catch or try to plow with the one side of the blade without it angled all the way back towards the machine. The plow will angle all the way back until it bottoms out the cylinder or I stop driving forwards. The first time this happened, I blew the threaded hose connection to the iso coupler apart. Now the hose will visibly straighten from the pressure but I try and avoid plowing with just the edge of the plow. Maybe I'm over thinking the performance of the plow, but I sure would like to be able to not have to worry about the plow carrying on like this. My tractor only slightly outweighs a full size truck but I'm only plowing less than 5 mph right now. (10-11klbs in case it helps anyone) As soon as the obstruction is backed away from, the plow goes back to where i had it positioned.

Do I need to replace the cylinders?
Should I look at the locking cylinders that boss has for their back dragging V-plows? They look to be around 250-350 a piece.
I have heard that the fisher? plows use double acting cylinders. Would those DA cylinders help?
Would full size tie rod cylinders fix my issue?


I never had this problem with the 7.5' meyer that I pushed with the Kubota. I'm already frustrated that the plow trips constantly and I have to chase the plow frame to try and keep it level so it trips less. I have 4 springs on it now with two of them bottomed out of adjustment. I have room for two more so I think thats the next step. If the driveway and parking lot were level it would be fine. I'm half tempted to try and figure out how to convert to a snow pusher that doesn't trip at all.


The original plow attachment design that failed and did not follow the ground contour very well.

 

[RockyNY]

You need to plumb in a crossover relief valve. It diverts fluid to the opposite cylinder when one side goes over a preset amount of force. That's what I have on my Meyers 7.5'

 

[RedNeckRacin]

I think that will make my problem worse , not better but thanks. I want the plow to be more resistant not less to offset loading.

 

[kennyd]

I'd guess that your valve is now damaged, probably happened at the first incedent that ended up blow a fitting apart, that should tell you the kind of pressure the system was under just before it blew. A crossover relief would have prevented this from happening. There is no other place the fluid can cross over to let the plow move but in the valve.

 

[skyhook]

I am by no means an expert on hydraulics,
but what I think the OP is trying to say is....
He wants his blade to stay "straight" when using the side of it, he doesn't want it to angle,
or not to angle so easily. Along with the front springs are "tripping" to easily.

I was going to say that maybe the rear relief is set to low for the blade cylinders but then noticed the hose blew? I don't know what the answer is, :confused2:
As for the front blade springs, you would think that 4 is plenty. Maybe the blade is angled improperly, cutting into the ground too much.

 

[RedNeckRacin]

Skyhook, your right. I want it to be more resistant to angling unless I angle it with the hydraulics. As it is now, once I back away from the bank the plow returns to the original position so its not bypassing the valve in the tractor. I do not want a cross over relief. I think that this would only make the problem more pronounced.


Kenny-The threads actually stripped off the iso fitting. I had thread sealer on the threads and I may have gotten over ambitious with it the last time. I have since bought a new fitting and only wrapped the threads enough to get the tape to stick.


Yes, the front springs are tripping to easily. That is a whole different problem that I was venting. It is drilled for a third set of spring so I think I'm going to add them.

 

[ddbackhoe]

Skyhook, your right. I want it to be more resistant to angling unless I angle it with the hydraulics. As it is now, once I back away from the bank the plow returns to the original position so its not bypassing the valve in the tractor. I do not want a cross over relief. I think that this would only make the problem more pronounced.


Kenny-The threads actually stripped off the iso fitting. I had thread sealer on the threads and I may have gotten over ambitious with it the last time. I have since bought a new fitting and only wrapped the threads enough to get the tape to stick.


Yes, the front springs are tripping to easily. That is a whole different problem that I was venting. It is drilled for a third set of spring so I think I'm going to add them.

From what little I know, you're missing check valves and a crossover relief. The check valves "lock" the cylinders in place and the relief will let fluid move around if you hit something hard.
This picture may help. (from Myers http://ww2.meyerproducts.com/upload/forms/1-562 R16.pdf)

 

[RockyNY]

Sounds to me like you have 2 options. 1) install a crossover relief valve or 2) lose the hydraulic angle.
The crossover valves have adjustable relief pressure settings, you set them high enough to not angle under normal plowing conditions, but low enough to angle when you strike a solid object. Otherwise, you're always going to risk blowing hoses when you hit something with the corner of the plow.

 

[RedNeckRacin]

From what little I know, you're missing check valves and a crossover relief. The check valves "lock" the cylinders in place and the relief will let fluid move around if you hit something hard.
This picture may help. (from Myers http://ww2.meyerproducts.com/upload/forms/1-562 R16.pdf)

I didn't think I needed check valves since the valving on the tractor wouldn't let any oil bypass. I was thinking of the boss sa cylinders that had the internal checks but I was unaware that I could get external ones to function to allow the cylinder to retract? The part that worries me is that the cylinder that is not under pressure is extending.

Sounds to me like you have 2 options. 1) install a crossover relief valve or 2) lose the hydraulic angle.
The crossover valves have adjustable relief pressure settings, you set them high enough to not angle under normal plowing conditions, but low enough to angle when you strike a solid object. Otherwise, you're always going to risk blowing hoses when you hit something with the corner of the plow.

1. No. I think this will make my problem worse. I want it to hold the angle, not yield. I'm not expecting it to act like a fixed dozer blade that will tear through anything, but I should be able to shove a windrow of decent size with my setup.
2. No. If anything, I'm going to put bigger DA cylinders on so I can get the plow to function properly and overcome the force of the plow with stronger cylinders.

 

[ddbackhoe]

:

I didn't think I needed check valves since the valving on the tractor wouldn't let any oil bypass. I was thinking of the boss sa cylinders that had the internal checks but I was unaware that I could get external ones to function to allow the cylinder to retract? The part that worries me is that the cylinder that is not under pressure is extending.

May have bee useful to attach the correct picture :ashamed:
Right. Both cylinder rods are actually moving, one compressing and one extending, they have to because they are mechanically tied together. The control valve isn't holding back the fluid when the one side rod is being compressed (over pressure is leaking past the seals). Check valves in the circuit will stop the flow of fluid in either direction. A pilot operated check valve will allow flow in two directions when opened. With the check valves installed, the volume of fluid is contained preventing the left or right from compressing.
In a single acting cylinder, the fluid is "pushed" from the bottom to extend the rod. Retraction is done by releasing the pressure and allowing gravity (or external force) to compress the rod (floor jack uses a sa cylinder). A double acting cylinder uses the fluid to "push" the rod in both directions. Adding double acting cylinders will most likely not solve the problem.

Valving Technology